1. Field of the Invention
The present invention relates generally to pressure relief valves and more specifically to such valves which include provisions for manual opening thereof.
2. Description of the Prior Art
Manually operable poppet-type relief valves are often used for limiting the pressure in and for depressurizing and draining fluid from enclosures. In such applications the valves generally employ a spring loaded poppet operating conventionally in response to pressure increases in the enclosure to bleed off fluid to effect the pressure limiting function. Draining is accomplished through manually displacing the poppet to overcome the closing force of its load spring and thereby open the valve.
Certain disadvantages have been noted, however, in the use of the prior art valves. One disadvantage has been that the mechanisms employed to manually open the valves have been operable by manual displacement in a single direction, thereby allowing inadvertent opening of the valves.
Another disadvantage in certain prior art valves has been that the opening mechanisms have employed means for connection to the valve poppet which leave exposed beyond the major structural confines of the valve, elements rigidly fixed to the poppet itself, thereby permitting interference with its freedom of operation.
Still another disadvantage has been that the prior art valves have been expensive to produce.